1. Field of the Invention
The present invention relates to a webbing wind-up force reducing apparatus for use in a seatbelt system designed to protect an occupant of a vehicle in an emergency situation of the vehicle, the apparatus being employed to reduce the webbing wind-up force which acts such as to apply pressure to the body of the occupant.
2. Description of the Related Art
A typical seatbelt system is arranged such that an occupant restraining webbing can be fully wound up on a webbing take-up shaft by means of the biasing force of a spiral spring. With this arrangement, when an occupant has the webbing fastened, the webbing tension unnecessarily increases and makes the occupant feel the pressure from the webbing. In order to overcome this advantage, a webbing wind-up force reducing apparatus has been devised which is provided with a ratchet wheel which rotates together with the webbing take-up shaft in one unit, and a pawl which is engageable with the ratchet wheel, whereby the webbing take-up shaft is prevented from rotating in the direction in which the webbing is wound up when the occupant has the webbing fastened in a normal state of the vehicle (see the specification of Japanese Patent Laid-Open No. 92233/1984). Provision of this apparatus on a webbing retractor eliminates any possibility of the occupant feeling the pressure from the webbing when he has the webbing fastened in a normal state of the vehicle.
The above-described conventional apparatus, however, suffers from the disadvantage that it is necessary to cause the pawl to engage with the ratchet wheel by the action of an actuator and to maintain this engaged state for a long period of time, which fact necessitates to supply the actuator with a relatively large amount of electric power.